Typically, battery chargers are implemented with a conventional Alternating Current (AC) or Direct Current (DC) connector which is connected to a power source. When a user wants to charge a battery, for example a power tool battery, it is inserted into the charger and the charger draws power from a power source, i.e. an electrical outlet. The prior solutions for battery charging typically require a battery charger connected to an electrical outlet. The problem with electrical outlet solutions, is when there is no readily available power source, the user is left with no options for charging their batteries. What is desired, is a way of charging a plurality of battery types and devices at or near the resonant frequency in order to improve charging efficiency, speed charging time, and extend the lifetime of the battery, while providing a mobile power source in the field.